1. Field of the Invention
The subject matter described herein relates generally to combustors, and more particularly to fuel nozzles in combustors.
2. Description of Related Art
Gas turbine systems are widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor, a combustor, and a turbine. In a conventional gas turbine system, compressed air is provided from the compressor to the combustor. The air entering the combustor is mixed with fuel and combusted. Hot gases of combustion flow from the combustor to the turbine to drive the gas turbine system and generate power.
Natural gas is typically utilized as a primary fuel for a gas turbine system. In some systems, the natural gas is flowed through a fuel nozzle and mixed with working fluid to provide a working fluid/fuel mixture for combustion. In other systems, the combustor may be part of a low-oxygen and/or closed loop systems, and the working fluid may be a low-oxygen working fluid. In these known systems, fuel and an oxidizer may be flowed through a fuel nozzle and mixed together with working fluid to provide an appropriate mixture for combustion. Frequently, fuel and oxidizer may be flowed through a fuel nozzle in a near-stochiometric ratio before being mixed with any significant amount of working fluid to ensure high efficiency combustion.
Known fuel nozzles and combustors may not adequately mix the fuel and the working fluid or oxidizer before combustion. This may result in relatively low efficiency combustion. Specifically, in low-oxygen systems, inadequate mixing of the fuel and oxidizer may result in longer residence times of the fuel and oxidizer in the combustor, which may cause diluting of the fuel and oxidizer by the low-oxygen working fluid. This diluting may lower the combustion efficiency.
In view of the foregoing, there exists a need for an improved fuel nozzle for a combustor and method for operating a combustor. For example, a fuel nozzle and method that provide improved mixing of fuel with working fluid and/or oxidizer and improves combustion efficiency would be advantageous. In particular, a fuel nozzle and method that provide improved combustion efficiency in low-oxygen systems would be desired.